/// <summary>
/// Generates a string based on the given regular expression
/// if any nodes are prepended with \i, then one of these nodes will be chosen
/// at random to be invalidated
/// </summary>
/// <param name="random">Random object to use for generation</param>
/// <param name="regex">Regular expression used to generate the string</param>
/// <returns>generated string</returns>
public static string NextString(Random random, string regex)
{
//reset the static variables
RECompiler.IsInvalidSection = false;
RECompiler.InvalidNode = null;
RECompiler.InvalidableNodes.Clear();
//construct the RegEx tree
RECompiler compiler = new RECompiler();
RENode node = compiler.Compile(regex);
//search for a signal to invalidate a node
if (regex.IndexOf("\\i", StringComparison.Ordinal) != -1)
{
//something should have been invalidated
//select a node to invalidate
if (RECompiler.InvalidableNodes.Count == 0)
{
throw new ArgumentException("Asked to generate invalid: Impossible to invalidate");
}
RECompiler.InvalidNode = RECompiler.InvalidableNodes[random.Next(RECompiler.InvalidableNodes.Count)];
//Mark REOrNodes and RERepeatNodes to ensure that the invalid node will be part of the string
RECompiler.InvalidNode.ReservePath(null);
}
//generate and return the string
string result = node.Generate(random);
if (RECompiler.InvalidNode != null)
{
//confirm that the generated string is invalid (e.g. [a-z]|[^a-z] will always fail)
Regex compare = new Regex("^" + regex.Replace("\\i", "") + "$");
if (compare.IsMatch(result))
{
throw new ArgumentException(regex + ": Did not generate invalid string: " + result);
}
}
return result;
}
//Compile [:alpha:] [:punct:] etc
internal RENode CompileMacro(int index, int len)
{
AssertParse(len >= 0, "Cannot parse macro.");
string substr = mRegex.ToString().Substring(index, len);
string expanded = null;
switch (substr)
{
case "alnum": expanded = "[a-zA-Z0-9]"; break;
case "alpha": expanded = "[a-zA-Z]"; break;
case "upper": expanded = "[A-Z]"; break;
case "lower": expanded = "[a-z]"; break;
case "digit": expanded = "[0-9]"; break;
case "xdigit": expanded = "[A-F0-9a-f]"; break;
case "space": expanded = "[ \t]"; break;
case "print": expanded = "[\\x20-\\x7F]"; break;
case "punct": expanded = "[,;.!'\"]"; break;
case "graph": expanded = "[\\x80-\\xFF]"; break;
case "cntrl": expanded = "[]"; break;
case "blank": expanded = "[ \t\r\n\f]"; break;
case "guid": expanded = "[A-F0-9]{8}(-[A-F0-9]{4}){3}-[A-F0-9]{12}"; break;
default: AssertParse(false, "Cannot parse macro."); break;
}
RECompiler subcompiler = new RECompiler();
return subcompiler.Compile(expanded);
}